As digitalization and informatization are accelerated, a lot of IT is used in daily life and much development in display technology of IT equipment is underway. As representative examples of a flat-panel display, there are LCDs, PDPs, OLEDs, etc. Thereamong, LCDs are most common.
Since an LCD in which liquid crystal and semiconductor technology are combined has advantages such as light weight and low consumption power, it is currently, broadly used in large TVs, PC monitors, display devices of various measurement equipment, PMP or MP3 equipment, navigators of vehicles, cellular phones, etc.
In order to realize large high-quality LCDs, a wide viewing angle, high brightness, a high contrast ratio, a fast response rate, etc. are required. As broadly used modes among currently known LCD operation modes, there are twisted nematic (TN), super twisted nematic (STN), vertical alignment (VA) and in-plane switching (IPS).
Stick-type liquid crystal molecules used in such LCDs are orientated in a given direction on a polymer alignment layer. Such orientation causes change in apparent Δnd of liquid crystal according to a viewing angle in each LCD, thus limiting wide viewing angles in LCDs.
When liquid crystal molecule arrangement is changed by application of an electric field, proceeding light meets with liquid crystal molecule at different angles, and thus, a polarization state of transmitted light varies. As a result, when transmitted light passes through a polarization plate of an LCD surface, some light is leaked. In this case, luminance between a front side and an inclined angle is different or contrast reversal occurs.
Various attemps have been made to overcome such phenomena and secure a wide viewing angle. Thereamong, a method using a compensation film is currently, relatively broadly used. A compensation film has a changed value in a phase difference according to increase of a viewing angle and performs compensation using an opposite direction film.
To correspond to various LCD modes, a variety of compensation films are required. Currently, compensation film technology uses a thick oriented film and, is limited to liquid crystal films. When, as a material of such a compensation film, reactive liquid crystal is used, a highly efficient compensation film may be realized. In order to realize a highly-efficient ultra-thin compensation film, there is an urgent need for reactive liquid crystal compounds having unique liquid crystal characteristics such as molecular orientation by forming a polymer network through photopolymerization, and superior thermostability and a simple preparation process. However, currently, commercially available reactive liquid crystal compounds have a complex preparation process in order to express unique liquid crystal characteristics and low thermostability.
As a conventional reactive liquid crystal compound, Korean Patent No. 10-1006145 discloses a discoid liquid crystal compound, represented by a formula given below, having various-size alkyl, polyethylene glycol, phenyl alkyl ester and phenyl polyethylene glycol ester chains as side chains from the center of triphenylene for temperature range control of a liquid crystal phase, and phenylacryloyl (cinnamoyl), naphthyl acryloyl and biphenyl acryloyl at side chain terminals for photocrosslinking at various wavelengths.

In addition, Korean Application Pub. No. 10-1069555 discloses a rod-type liquid crystal compound in which (1) phenyl or an acetylene functional group for providing high birefringence, (2) various-length alkyl as side chains for controlling a temperature range of a liquid crystal phase, and (3) acryloyl, methacryloyl, phenylacryloyl (cinnamoyl) or furylacryloyl as a terminal group for photocrosslinking reaction are introduced into the center of hydroquinone substituted with a high-birefringence mesogen compound containing a photoreactive group wherein a film may be formed through photocrosslinking reaction by ultraviolet (UV) irradiation.
In addition, Korean Application Pub. No. 10-2011-0104416 discloses a reactive mesogen compound represented by Formula P1-A1-(Z1-A2)n-P2 (wherein P1 and P2 are each independently selected from the group consisting of acrylate, methacrylate, vinyl, vinyloxy and epoxy, A1 and A2 are each independently selected from the group consisting of 1,4-phenylene and naphthalene-2,6-diyl, Z1 is one of COO—, OCO—and a single bond, and n is one of 0, 1 and 2.
Furthermore, Korean Application Pub. No. 10-2011-0112372 discloses a mesogen compound represented by formulas below.

However, conventional reactive mesogen compounds have problems such as a complex synthesis process, a low birefringence and low thermostability.
In particular, in order to satisfy requirements of a variety of compensation films in lcd displays, two types such as an oriented film and an orientation-coated reactive liquid crystal are used.
As a material of a compensation film orientation-coated with a reactive liquid crystal, a reactive liquid crystal having a high birefringence is required. In order to realize an ultra-thin compensation film, a reactive liquid crystal compound having a high birefringence is essential.
However, currently available reactive liquid crystal compounds for a compensation film have a low birefringence of less than 1.6.
Accordingly, the present inventors discovered a novel reactive mesogen compound having a simple synthesis process, superior thermostability and high birefringence, and a method of preparing the same, thus completing the present invention.